Processing materials with ion beams

ABSTRACT

Materials such as biomass (e.g., plant biomass, animal biomass, and municipal waste biomass) and hydrocarbon-containing materials are processed to produce useful products, such as fuels. For example, systems are described that can use feedstock materials, such as cellulosic and/or lignocellulosic materials and/or starchy materials, or oil sands, oil shale, tar sands, bitumen, and coal to produce altered materials such as fuels (e.g., ethanol and/or butanol). The processing includes exposing the materials to an ion beam.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 61/073,680, filed Jun. 18, 2008. The complete disclosure of thisprovisional application is hereby incorporated by reference herein.

BACKGROUND

Biomass, particularly biomass waste, and hydrocarbon-containingmaterials, such as oil sands, oil shale, tar sands, bitumen, and coal,are widely available. It would be useful to derive materials and fuel,such as ethanol, from biomass and hydrocarbon-containing material.

SUMMARY

Biomass and hydrocarbon-containing material can be processed to alterits structure at one or more levels. The processed materials can then beused as a source of altered materials and/or fuel.

Many embodiments of this application use Natural Force™ Chemistry (NFC).Natural Force™ Chemistry methods use the controlled application andmanipulation of physical forces, such as particle beams, gravity, light,etc., to create intended structural and chemical molecular change.

Methods for changing a molecular and/or a supramolecular structure of amaterial, e.g., any biomass material, can include treating the materialwith radiation. In particular, the radiation can include particles,particularly charged particles (e.g., accelerated charged particles).Charged particles include ions, such as positively charged ions, such asprotons, carbon or oxygen ions. The radiation can be applied in anamount sufficient to change the molecular structure and/orsupramolecular structure of the material. The radiation can also beapplied to produce one or more products from the material. The materialcan in some cases include carbohydrates or materials that includecarbohydrates, e.g., cellulosic materials, lignocellulosic materials,starchy materials, or mixtures of any biomass materials.

Particles having a different charge than electrons and/or particlesheavier than electrons can be utilized for the irradiation. For example,protons, helium nuclei, argon ions, silicon ions, neon ions, carbonions, phosphorus ions, oxygen ions or nitrogen ions can be utilized tomodify the structure of the biomass, e.g., breakdown the molecularweight or increase the molecular weight of the biomass. In someembodiments, heavier particles can induce higher amounts of chainscission in comparison to electrons or photons. In addition, in someinstances, positively charged particles can induce relatively largeamounts of chain scission due to their acidity. In certain instances,negatively charged particles can induce relatively large amounts ofchain scission due to their alkalinity.

Accordingly, in one aspect, the invention features a method of changinga molecular structure of a material, e.g., a biomass material or ahydrocarbon-containing material, by producing an ion beam comprising afirst distribution of ion energies having a full width at half maximumof w; adjusting the energies of at least some of the ions to produce asecond distribution of ion energies in the ion beam having a full widthat half maximum of more than w; and exposing the material to theadjusted ion beam. The energies of at least some of the ions can beadjusted based on, for example, a thickness of the material.

In another aspect, the invention features a method of changing amolecular structure of a material, e.g., a biomass material or ahydrocarbon-containing material, by producing an ion beam comprising adistribution of ion energies having a full width at half maximum of w;directing the ion beam to pass through a scattering element configuredto increase the full width at half maximum of the distribution of ionenergies to a value larger than w; and exposing the material to the ionbeam after the ion beam has passed through the scattering element.

In yet another aspect, the invention features a method of changing amolecular structure of a material, e.g., a biomass material or ahydrocarbon-containing material, by producing an ion beam having adistribution of ion energies, the distribution having a most probableenergy E; filtering the ion beam to remove at least some ions having anenergy less than E from the ion beam; and exposing the material to thefiltered ion beam.

In a further aspect, the invention features a method of changing amolecular structure of a material, e.g., a biomass material or ahydrocarbon-containing material, by producing an ion beam having adistribution of ion energies; adjusting the distribution of ion energiesbased on an expected ion dose profile in the material; and exposing thematerial to the adjusted ion beam.

The invention also features a method of changing a molecular structureof a material, e.g., a biomass material or a hydrocarbon-containingmaterial, by producing an ion beam having a distribution of ionenergies; adjusting the distribution of ion energies based on a fullwidth at half maximum (FWHM) of a Bragg peak of an expected ion doseprofile in the material; and exposing the material to the adjusted ionbeam, wherein the adjusting comprises increasing the FWHM to reduce adifference between a thickness of the biomass material and the FWHM.

In some cases, following the adjusting, the difference between thethickness of the material and the FWHM is 0.01 cm or less.

In yet another aspect, the invention features a method of changing amolecular structure of a material by producing a first ion beam from anion source, the first ion beam having a first average ion energy;exposing the material to the first ion beam; adjusting the ion source toproduce a second ion beam having a second average ion energy differentfrom the first average ion energy; and exposing the material to thesecond ion beam.

In some cases, the method further includes repeating the adjusting andexposing to expose the material to a plurality of ion beams havingdifferent average ion energies. The composition of the first and secondion beams can be the same.

In a further aspect, the invention features a method of changing amolecular structure of a material by:

producing a first ion beam from an ion source, the first ion beam havinga first average ion energy corresponding to a first position of a Braggpeak in an expected ion dose profile of the material;

exposing the material to the first ion beam;

adjusting the ion source to produce a second ion beam having a secondaverage ion energy corresponding to a second position of the Bragg peakdifferent from the first position; and

exposing the material to the second ion beam.

In some cases, the method further includes repeating the adjusting andexposing to expose the material to a plurality of ion beamscorresponding to different positions of the Bragg peak. The compositionof the first and second ion beams can be the same.

In yet another aspect, the invention features a method of changing amolecular structure of a material by producing an ion beam from an ionsource, the ion beam comprising a first type of ions and a second typeof ions different from the first type of ions; and exposing the materialto the ion beam.

For example, the first type of ions can comprise hydrogen ions and thesecond type of ions can comprise carbon ions, or the first type of ionscan comprise hydrogen ions and the second type of ions can compriseoxygen ions, or the first and second types of ions can comprise at leastone of protons and hydride ions. In some cases the first and secondtypes of ions each have ion energies between 0.01 MeV and 10 MeV.

In another aspect, the invention features a method of changing amolecular structure of a material by producing a ion beam having adivergence angle of 10 degrees or more, e.g., 20 degrees or more, at asurface of the material; and exposing the biomass material to the ionbeam.

In yet another aspect, the invention features a method of changing amolecular structure of a material by adjusting an ion source to producean ion beam having an average ion current and an average ion energy; andexposing the material to the ion beam, wherein the ion source isadjusted based on an expected ion dose profile in the material andwherein each portion of the material receives a radiation dose ofbetween 0.01 Mrad and 50 Mrad, e.g., between 0.1 Mrad and 20 Mrad, as aresult of exposure to the ion beam.

In another aspect, changing a molecular structure of a material includesproducing an ion beam including a first distribution of ion energieshaving a full width at half maximum of W, adjusting the energies of atleast some of the ions based on a thickness of a hydrocarbon-containingmaterial to produce a second distribution of ion energies in the ionbeam having a full width at half maximum of more than W, and exposingthe hydrocarbon-containing material to the adjusted ion beam. Thehydrocarbon-containing material can be selected from the groupconsisting of oil sands, oil shale, tar sands, bitumen, and coal.

In another aspect, changing a molecular structure of a material includesproducing an ion beam including a first distribution of ion energieshaving a full width at half maximum of W, adjusting the energies of atleast some of the ions to produce a second distribution of ion energiesin the ion beam having a full width at half maximum of more than W, andexposing the material to the adjusted ion beam.

In some instances, the material is a biomass material, a non-biomassmaterial, or any combination thereof. For example, the material can be ahydrocarbon-containing material such as oil sands, oil shale, tar sands,bitumen, coal, and other mixtures of hydrocarbons and non-hydrocarbonmaterial.

In some cases, the method further includes exposing the material to aplurality of electrons or to ultrasonic energy following exposure to theion beam.

Some implementations of any of the above-mentioned aspects of theinvention can include one or more of the following features. Adjustingthe energies of at least some of the ions can include adjusting based ona thickness of the material exposed to the ion beam. In some cases,adjusting the energies of at least some of the ions can includeadjusting based on an expected ion dose profile in the material.Adjusting can also include increasing a full width at half maximum of aBragg peak of an expected ion dose profile in the material enough toreduce a difference between a thickness of the material and the fullwidth at half maximum of the Bragg peak. Following adjusting, thedifference between the thickness of the material and the full width athalf maximum of the Bragg peak can be 0.01 centimeter or less.

The full width at half maximum of the second distribution can be largerthan w by a factor of 2.0 or more, e.g., by a factor of 4.0 or more.Adjusting the energies of at least some of the ions can includedirecting the ions to pass through a scattering element, e.g., ahemispherical analyzer. In some cases, the adjusted ion beam passesthrough a fluid prior to being incident on the material, e.g. throughair at a pressure of 0.5 atmospheres or more. The ion beam can includetwo or more different types of ions, e.g., hydrogen ions and carbon ionsor hydrogen ions and oxygen ions. The ion beam can include at least oneof protons and hydride ions. The average energy of the ions in the ionbeam can be between 0.01 MeV and 10 MeV.

Changing a molecular structure of a material, such as a biomassfeedstock or a hydrocarbon-containing material, as used herein, meanschanging the chemical bonding arrangement, such as the type and quantityof functional groups or conformation of the structure. For example, thechange in the molecular structure can include changing thesupramolecular structure of the material, oxidation of the material,changing an average molecular weight, changing an average crystallinity,changing a surface area, changing a degree of polymerization, changing aporosity, changing a degree of branching, grafting on other materials,changing a crystalline domain size, or changing an overall domain size.

Biomass or hydrocarbon-containing material can be exposed to radiation,for example an ion beam, e.g., a beam according to one or more of theconfigurations described herein. The beam and duration of exposure canbe chosen such that the molecular structure of the material is altered.The material can be treated prior to and/or after the exposure. Theexposed material can be used in a variety of applications, includingfermentation and the production of composite materials.

Also featured are systems and devices for treating materials withradiation as disclosed herein. An exemplary system includes a reservoirfor biomass, a device that produces a particle beam, e.g., as describedherein, and a conveyance device for moving biomass from the reservoir tothe device that produces a particle beam.

Implementations may include one or more of any of the features describedherein.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, suitable methods andmaterials are described below. All publications, patent applications,patents, and other references mentioned herein are incorporated byreference in their entirety. In case of conflict, the presentspecification, including definitions, will control. In addition, thematerials, methods, and examples are illustrative only and not intendedto be limiting.

This application incorporates by reference herein the entire contents ofInternational Application No. PCT/US2007/022719, filed Oct. 26, 2007,and U.S. Provisional Application No. 61/049,406, filed Apr. 30, 2008.

Other features and advantages will be apparent from the followingdetailed description, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating conversion of biomass intoproducts and co-products.

FIG. 2 is a schematic diagram showing dose profiles for ions, electrons,and photons in a condensed-phase material.

FIG. 3 is a schematic diagram of an ion beam exposure system.

FIGS. 4A and 4B are schematic diagrams showing ion beam energydistributions.

FIG. 4C is a schematic diagram showing ion dose profiles in an exposedsample.

FIG. 5 is a schematic diagram of a scattering element that includesmultiple sub-regions.

FIG. 6 is a schematic diagram of an ion beam exposure system thatincludes an ion filter.

FIGS. 7A-C are schematic diagrams showing energy distributions forunfiltered and filtered ion beams.

FIG. 8 is a schematic diagram showing three ion dose profilescorresponding to exposure of a sample to ion beams having differentaverage energies.

FIG. 9A is a schematic diagram showing a net ion dose profile for anexposed sample based on the three ion dose profiles of FIG. 8.

FIG. 9B is a schematic diagram showing three different ion dose profilescorresponding to ion beams of different average energy and ion current.

FIG. 9C is a schematic diagram showing a net ion dose profile based onthe three ion dose profiles of FIG. 9B.

FIG. 10A is a schematic diagram showing three different ion doseprofiles corresponding to exposure of a sample to beams of threedifferent types of ions.

FIG. 10B is a schematic diagram showing a net ion dose profile based onthe three ion dose profiles of FIG. 10A.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Treating biomass with radiation is useful for producing fuel andproducts. Generally biomass material is physically prepared beforetreatment with radiation. The material can be prepared so as to renderit more uniform, e.g., to reduce particle size, to alter water content,to control viscosity, and so forth. The material is treated withradiation to alter the molecular and/or supra-molecular structure. Inaddition, the material can be treated in other ways, for example, withsonication, oxidation, pyrolysis, and steam explosion. The resultingmaterial can be stored or used in a variety ways.

One application is fermentation to produce a combustible product, suchas an alcohol. Microorganisms can be combined with the resultingmaterial, and, optionally, other ingredients. The combination isfermented and product is recovered. For example, alcohols can berecovered by distillation.

In some embodiments, the radiation is applied on a large scale, forexample to a batch of at least 50 kg, 100 kg, or 500 kg. The treatmentcan also be applied in a continuous or semi-continuous mode, forexample, to material that moves under a radiation beam, e.g., so as toprocess at least 100, 500, 1000, 5000, or 20000 kg per hour.

A variety of biomass materials can be used as a starting material.Examples of biomass include plant biomass, animal biomass, and municipalwaste biomass. Biomass also includes feedstock materials such ascellulosic and/or lignocellulosic materials.

Often biomass is material that includes a carbohydrate, such ascellulose. Generally, any biomass material that is or includescarbohydrates composed entirely of one or more saccharide units or thatinclude one or more saccharide units can be processed by any of themethods described herein. For example, the biomass material can becellulosic or lignocellulosic materials, or starchy materials, such askernels of corn, grains of rice or other foods.

Additional examples of biomass materials include paper, paper products,wood, wood-related materials, particle board, grasses, rice hulls,bagasse, cotton, jute, hemp, flax, bamboo, sisal, abaca, straw, corncobs, rice hulls, coconut hair, algae, seaweed, cotton, syntheticcelluloses, or mixtures of any of these. Still other examples aredescribed in WO 2008/073186, filed Oct. 26, 2007, and U.S. Ser. No.12/429,045, filed Apr. 23, 2009.

Various biomass materials are often readily available, but—unlesspretreated—can sometimes be difficult to process, e.g., by fermentation,or can give sub-optimal yields at a slow rate. In the methods describedherein, feedstock materials can be first physically prepared forprocessing, often by size reduction of raw feedstock materials.Physically prepared feedstock can be pretreated or processed using oneor more of radiation, sonication, oxidation, pyrolysis, and steamexplosion. The various pretreatment systems and methods can be used incombinations of two, three, or even four of these technologies.Combinations of various pretreatment methods are generally disclosed inWO 2008/073186, for example.

In some cases, to provide materials that include a carbohydrate, such ascellulose, that can be converted by a microorganism to a number ofdesirable products, such as a combustible fuels (e.g., ethanol, butanolor hydrogen), feedstocks that include one or more saccharide units canbe treated by any one or more of multiple processes. Other products andco-products that can be produced include, for example, human food,animal feed, pharmaceuticals, and nutriceuticals. Examples of otherproducts are described in U.S. Ser. Nos. 12/417,900, 12/417,707,12/417,720, and 12/417,731, all of which were filed Apr. 3, 2009.

Where the biomass is or includes a carbohydrate it may include, forexample, a material having one or more β-1,4-linkages and having anumber average molecular weight between about 3,000 and 50,000. Such acarbohydrate is or includes cellulose (I), which is derived from(β-glucose 1) through condensation of β(1→4)-glycosidic bonds. Thislinkage contrasts itself with that for α(1→4)-glycosidic bonds presentin starch and other carbohydrates.

Starchy materials include starch itself, e.g., corn starch, wheatstarch, potato starch or rice starch, a derivative of starch, or amaterial that includes starch, such as an edible food product or a crop.For example, the starchy material can be arracacha, buckwheat, banana,barley, cassava, kudzu, oca, sago, sorghum, regular household potatoes,sweet potato, taro, yams, or one or more beans, such as favas, lentilsor peas. Blends of any one or more starchy material are also starchymaterials. In particular embodiments, the starchy material is derivedfrom corn. Various corn starches and derivatives are described in “CornStarch,” Corn Refiners Association (11th Edition, 2006).

Biomass materials that include low molecular weight sugars can, e.g.,include at least about 0.5 percent by weight of the low molecular sugar,e.g., at least about 2, 3, 4, 5, 6, 7, 8, 9, 10, 12.5, 25, 35, 50, 60,70, 80, 90 or even at least about 95 percent by weight of the lowmolecular weight sugar. In some instances, the biomass is composedsubstantially of the low molecular weight sugar, e.g., greater than 95percent by weight, such as 96, 97, 98, 99 or substantially 100 percentby weight of the low molecular weight sugar.

Biomass materials that include low molecular weight sugars can beagricultural products or food products, such as sugarcane and sugarbeets or an extract therefrom, e.g., juice from sugarcane, or juice fromsugar beets. Biomass materials that include low molecular weight sugarscan be substantially pure extracts, such as raw or crystallized tablesugar (sucrose). Low molecular weight sugars include sugar derivatives.For example, the low molecular weight sugars can be oligomeric (e.g.,equal to or greater than a 4-mer, 5-mer, 6-mer, 7-mer, 8-mer, 9-mer or10-mer), trimeric, dimeric, or monomeric. When the carbohydrates areformed of more than a single repeat unit, each repeat unit can be thesame or different.

Specific examples of low molecular weight sugars include cellobiose,lactose, sucrose, glucose and xylose, along with derivatives thereof. Insome instances, sugar derivatives are more rapidly dissolved in solutionor utilized by microbes to provide a useful material, such as ethanol orbutanol.

Combinations of any biomass materials described herein (e.g.,combinations of any biomass materials, components, products, and/orco-products generated using the methods described herein) can beutilized for making any of the products described herein, such asethanol. For example, blends of cellulosic materials and starchymaterials can be utilized for making products.

Fuels and other products (e.g., ethanol, bioethanol, other alcohols, andother combustible hydrocarbons) produced via the methods disclosedherein can be blended with other hydrocarbon-containing species. Forexample, ethanol produced using any of the methods disclosed herein canbe blended with gasoline to produce “gasohol,” which can be used ascombustible fuel in a wide variety of applications, including automobileengines.

Biomass Treatment Processes

FIG. 1 shows a system 100 for converting biomass, particularly biomasswith significant cellulosic and lignocellulosic components and/orstarchy components, into useful products and co-products. System 100includes a feed preparation subsystem 110, a pretreatment subsystem 114,a primary process subsystem 118, and a post-processing subsystem 122.Feed preparation subsystem 110 receives biomass in its raw form,physically prepares the biomass for use as feedstock by downstreamprocesses (e.g., reduces the size of and homogenizes the biomass), andstores the biomass both in its raw and feedstock forms.

Biomass with significant cellulosic and/or lignocellulosic components,or starchy components can have a high average molecular weight andcrystallinity that be modified by one or more pretreatments tofacilitate use of the material.

Pretreatment subsystem 114 receives feedstock from the feed preparationsubsystem 110 and prepares the feedstock for use in primary productionprocesses by, for example, reducing the average molecular weight andcrystallinity of the feedstock and/or increasing the surface area and/orporosity of the feedstock. In some cases, the pre-treated biomassmaterial has a low moisture content, e.g., less than about 7.5, 5, 3,2.5, 2, 1.5, 1, or 0.5 percent water by weight. Moisture reduction canbe achieved, e.g., by drying biomass material. Pretreatment processescan avoid the use of harsh chemicals such as strong acids and bases.

Primary process subsystem 118 receives pretreated feedstock frompretreatment subsystem 114 and produces useful products (e.g., ethanol,other alcohols, pharmaceuticals, and/or food products). Primaryproduction processes typically include processes such as fermentation(e.g., using microorganisms such as yeast and/or bacteria), chemicaltreatment (e.g., hydrolysis), and gasification.

In some cases, the output of primary process subsystem 118 is directlyuseful but, in other cases, the output requires further processingprovided by post-processing subsystem 122. Post-processing subsystem 122provides further processing to product streams from primary processsystem 118 (e.g., distillation and denaturation of ethanol) as well astreatment for waste streams from the other subsystems. In some cases,the co-products of subsystems 114, 118, 122 can also be directly orindirectly useful as secondary products and/or in increasing the overallefficiency of system 100. For example, post-processing subsystem 122 canproduce treated water to be recycled for use as process water in othersubsystems and/or can produce burnable waste which can be used as fuelfor boilers producing steam and/or electricity. In general,post-processing steps can include one or more steps such as distillationto separate different components, wastewater treatment (e.g., screening,organic equalization, sludge conversion), mechanical separation, and/orwaste combustion.

Ion Beam Systems for Biomass Pretreatment

Ion beam pretreatment (e.g., exposure to ions) of biomass can be aparticularly efficient, economical, and high-throughput treatmentmethod. Ion beam pretreatment generally includes exposing biomass(mechanically processed, or unprocessed) to one or more different typesof ions generated in one or more ion sources. The ions can beaccelerated in accelerator systems that are coupled to the ion sources,and can produce ions with varying energies and velocities. Typically, inion-based pretreatment, ions are not accelerated to sufficient energiesto cause large amounts of x-ray radiation to be produced. Accordingly,vaulting and shielding requirements for ion sources can be considerablyrelaxed relative to similar requirements for electron sources.

When ion beam radiation is utilized, it can be applied to any samplethat is dry or wet, or even dispersed in a liquid, such as water. Forexample, ion beam irradiation can be performed on cellulosic and/orlignocellulosic material in which less than about 25 percent by weightof the cellulosic and/or lignocellulosic material has surfaces wettedwith a liquid, such as water. In some embodiments, ion beam irradiatingis performed on cellulosic and/or lignocellulosic material in whichsubstantially none of the cellulosic and/or lignocellulosic material iswetted with a liquid, such as water.

When ion beam irradiation is utilized, it can be applied while thecellulosic and/or lignocellulosic material is exposed to air,oxygen-enriched air, or even oxygen itself, or blanketed by an inert gassuch as nitrogen, argon, or helium. When oxidation of the biomassmaterial is desired, an oxidizing environment is utilized, such as airor oxygen, and the properties of the ion beam source can be adjusted toinduce reactive gas formation, e.g., formation of ozone and/or oxides ofnitrogen. These reactive gases react with the biomass material, alone ortogether with incident ions, to cause degradation of the material. As anexample, when ion beam exposure of biomass is utilized, the biomass canbe exposed to ions under a pressure of one or more gases of greater thanabout 2.5 atmospheres, such as greater than 5, 10, 15, 20 or evengreater than about 50 atmospheres.

Ions that are incident on biomass material typically scatter from andionize portions of the biomass via Coulomb scattering. The interactionbetween the ions and the biomass can also produce energetic electrons(e.g., secondary electrons) that can further interact with the biomass(e.g., causing further ionization). Ions can be positively charged ornegatively charged, and can bear a single positive or negative charge,or multiple charges, e.g., one, two, three or even four or more charges.In instances in which chain scission is desired, positively chargedparticles may be desirable, in part, due to their acidic nature.

The ions to which biomass material is exposed can have the mass of aresting electron, or greater, e.g., 500, 1000, 1500, or 2000 or more,e.g., 10,000 or even 100,000 times the mass of a resting electron. Forexample, the ions can have a mass of from about 1 atomic unit to about150 atomic units, e.g., from about 1 atomic unit to about 50 atomicunits, or from about 1 to about 25, e.g., 1, 2, 3, 4, 5, 10, 12 or 15amu. Exemplary ions and ion accelerators are discussed in IntroductoryNuclear Physics, Kenneth S. Krane, John Wiley & Sons, Inc. (1988), KrstoPrelec, FIZIKA B 6 (1997) 4, 177-206, Chu, William T., “Overview ofLight-Ion Beam Therapy”, Columbus-Ohio, ICRU-IAEA Meeting, 18-20 Mar.2006, Iwata, Y. et al., “Alternating-Phase-Focused IH-DTL for Heavy-IonMedical Accelerators”, Proceedings of EPAC 2006, Edinburgh, Scotland,and Leitner, C. M. et al., “Status of the Superconducting ECR Ion SourceVenus”, Proceedings of EPAC 2000, Vienna, Austria.

A wide variety of different types of ions can be used to pretreatbiomass material. For example, protons, helium nuclei, argon ions,silicon ions, neon ions, carbon ions, phosphorus ions, oxygen ions ornitrogen ions can be utilized. In some embodiments, the ions can inducehigher amounts of chain scission than an equivalent dose of electrons.In some instances, positively charged ions can induce higher amounts ofchain scission and/or other processes than negatively charged ions dueto their acidity. Alternatively, in certain embodiments, depending uponthe nature of the biomass, negatively charged ions can be more effectivethan positively charged ions at inducing chain scission and/or otherprocesses, due to their alkaline nature.

Following generation and/or acceleration, the average energy of ions inan ion beam can be from about 1.0 MeV/atomic unit to about 6,000MeV/atomic unit, e.g., from about 3 MeV/atomic unit to about 4,800MeV/atomic unit, or from about 10 MeV/atomic unit to about 1,000MeV/atomic unit.

In general, many different types of ions can be used to irradiatebiomass materials. For example, in some embodiments, ion beams caninclude relatively light ions, such as protons and/or helium ions. Incertain embodiments, the ion beams can include moderately heavier ions,such as carbon ions, nitrogen ions, oxygen ions, and/or neon ions. Insome embodiments, ion beams can include still heavier ions, such asargon ions, silicon ions, phosphorus ions, sodium ions, calcium ions,and/or iron ions.

In certain embodiments, ion beams used to irradiate biomass materialscan include more than one different type of ion. For example, ion beamscan include mixtures of two or more (e.g., three, four, five, six ormore) different types of ions. Exemplary mixtures can include carbonions and protons, carbon ions and oxygen ions, nitrogen ions andprotons, and iron ions and protons. More generally, mixtures of any ofthe ions discussed herein (or any other ions) can be used to form ionbeams that are used to irradiate biomass. In particular, mixtures ofrelatively light and relatively heavier ions can be used in a single ionbeam, where each of the different types of ions has differenteffectiveness in irradiating different types of biomass materials.

In some embodiments, ion beams for irradiating biomass materials includepositively-charged ions. The positively charged ions can include, forexample, positively charged hydrogen ions (e.g., protons), noble gasions (e.g., helium, neon, argon), carbon ions, nitrogen ions, oxygenions, silicon atoms, phosphorus ions, and metal ions such as sodiumions, calcium ions, and/or iron ions. Without wishing to be bound by anytheory, it is believed that such positively-charged ions behavechemically as Lewis acid moieties when exposed to biomass materials,initiating and sustaining reactions such as cationic ring- andchain-opening scission reactions in an acidic and/or oxidativeenvironment.

In certain embodiments, ion beams for irradiating biomass materialsinclude negatively-charged ions. Negatively charged ions can include,for example, negatively charged hydrogen ions (e.g., hydride ions), andnegatively charged ions of various relatively electronegative nuclei(e.g., oxygen ions, nitrogen ions, carbon ions, silicon ions, andphosphorus ions). Without wishing to be bound by any theory, it isbelieved that such negatively-charged ions behave chemically as Lewisbase moieties when exposed to biomass materials, causing anionic ring-and chain-opening scission reactions in a basic and/or reducingenvironment.

In some embodiments, beams for irradiating biomass materials can includeneutral atoms. For example, any one or more of hydrogen atoms, heliumatoms, carbon atoms, nitrogen atoms, oxygen atoms, neon atoms, siliconatoms, phosphorus atoms, argon atoms, and iron atoms can be included inbeams that are used for irradiation of biomass materials. In general,mixtures of any two or more of the above types of atoms (e.g., three ormore, four or more, or even more) can be present in the beams.

The preceding discussion has focused on ion beams that includemononuclear ions and/or neutral particles (e.g., atomic ions and neutralatoms). Typically, such particles are the easiest—in energetic terms—togenerate, and parent particles from which these species are generatedmay be available in abundant supply. However, in some embodiments, beamsfor irradiating biomass materials can include one or more types of ionsor neutral particles that are polynuclear, e.g., including multiplenuclei, and even including two or more different types of nuclei. Forexample, ion beams can include positive and/or negative ions and/orneutral particles formed from species such as N₂, O₂, H₂, CH₄, and othermolecular species. Ion beams can also include ions and/or neutralparticles formed from heavier species that include even more nuclei,such as various hydrocarbon-based species and/or various inorganicspecies, including coordination compounds of various metals.

In certain embodiments, ion beams used to irradiate biomass materialsinclude singly-charged ions such as one or more of H⁺, H⁻, He⁺, Ne⁺,Ar⁺, C⁺, C⁻, O⁺, O⁻, N⁺, N⁻, Si⁺, Si⁻, P⁺, P⁻, Na⁺, Ca⁺, Fe⁺, Rh⁺, Ir⁺,Pt⁺, Re⁺, Ru⁺, and Os⁺. In some embodiments, ion beams can includemultiply-charged ions such as one or more of C²⁺, C³⁺, C⁴⁺, N³⁺, N⁵⁺,N³⁻, O²⁺, O²⁻, O₂ ²⁻, Si²⁺, Si⁴⁺, Si²⁻, and Si⁴⁻. In general, the ionbeams can also include more complex polynuclear ions that bear multiplepositive or negative charges. In certain embodiments, by virtue of thestructure of the polynuclear ion, the positive or negative charges canbe effectively distributed over substantially the entire structure ofthe ion. In some embodiments, the positive or negative charges can besomewhat localized over portions of the structure of the ions, by virtueof the electronic structures of the ions. Generally, ion beams used toirradiate biomass materials can include ions—both positive and/ornegative—of any of the molecular species disclosed herein, and the ionscan generally include one or multiple charges. The ion beams can alsoinclude other types of ions, positively and/or negatively charged,bearing one or multiple charges.

Ions and ion beams can be generated using a wide variety of methods. Forexample, hydrogen ions (e.g., both protons and hydride ions) can begenerated by field ionization of hydrogen gas and/or via thermal heatingof hydrogen gas. Noble gas ions can be generated by field ionization.Ions of carbon, oxygen, and nitrogen can be generated by fieldionization, and can be separated from one another (when they areco-generated) by a hemispherical analyzer. Heavier ions such as sodiumand iron can be produced via thermionic emission from a suitable targetmaterial. Suitable methods for generating ion beams are disclosed, forexample, in U.S. Provisional Application Nos. 61/049,406 and 61/073,665,and in U.S. Ser. No. 12/417,699.

A wide variety of different particle beam accelerators can be used toaccelerate ions prior to exposing biomass material to the ions. Forexample, suitable particle beam accelerators include Dynamitron®accelerators, Rhodotron® accelerators, static accelerators, dynamiclinear accelerators (e.g., LINACs), van de Graaff accelerators, andfolded tandem Pelletron accelerators. These and other suitableaccelerators are discussed, for example, in U.S. Provisional ApplicationNos. 61/049,406 and 61/073,665, and in U.S. Ser. No. 12/417,699.

In some embodiments, combinations of two or more of the various types ofaccelerators can be used to produce ion beams that are suitable fortreating biomass. For example, a folded tandem accelerator can be usedin combination with a linear accelerator, a Rhodotron® accelerator, aDynamitron® accelerator, a static accelerator, or any other type ofaccelerator to produce ion beams. Accelerators can be used in series,with the output ion beam from one type of accelerator directed to enteranother type of accelerator for additional acceleration. Alternatively,multiple accelerators can be used in parallel to generate multiple ionbeams for biomass treatment. In certain embodiments, multipleaccelerators of the same type can be used in parallel and/or in seriesto generate accelerated ion beams.

In some embodiments, multiple similar and/or different accelerators canbe used to generate ion beams having different compositions. Forexample, a first accelerator can be used to generate one type of ionbeam, while a second accelerator can be used to generate a second typeof ion beam. The two ion beams can then each be further accelerated inanother accelerator, or can be used to treat biomass.

Further, in certain embodiments, a single accelerator can be used togenerate multiple ion beams for treating biomass. For example, any ofthe accelerators discussed herein (and other types of accelerators aswell) can be modified to produce multiple output ion beams bysub-dividing an initial ion current introduced into the accelerator froman ion source. Alternatively, or in addition, any ion beam produced byany of the accelerators disclosed herein can include only a single typeof ion, or multiple different types of ions.

In general, where multiple different accelerators are used to produceone or more ion beams for treatment of biomass, the multiple differentaccelerators can be positioned in any order with respect to one another.This provides for great flexibility in producing one or more ion beams,each of which has carefully selected properties for treating biomass(e.g., for treating different components in biomass).

The ion accelerators disclosed herein can also be used in combinationwith any of the other biomass treatment steps. For example, in someembodiments, electrons and ions can be used in combination to treatbiomass. The electrons and ions can be produced and/or acceleratedseparately, and used to treat biomass sequentially (in any order) and/orsimultaneously. In certain embodiments, electron and ion beams can beproduced in a common accelerator and used to treat biomass. Certain ionaccelerators can be configured to produce electron beams as analternative to, or in addition to, ion beams. For example, Dynamitron®accelerators, Rhodotron® accelerators, and LINACs can be configured toproduce electron beams for treatment of biomass.

Moreover, pretreatment of biomass with ion beams can be combined withother biomass pretreatment methods such as sonication, pyrolysis,oxidation, steam explosion, and/or irradiation with other forms ofradiation (e.g., electrons, gamma radiation, x-rays, ultravioletradiation). In general, other pretreatment methods such assonication-based pretreatment can occur before, during, or afterion-based biomass pretreatment.

Exposure Conditions and Ion Beam Properties

In general, when a condensed medium is exposed to a charged particlebeam, the charged particles penetrate the medium and deposit within themedium at a distribution of depths below the surface upon which theparticles are incident. It has generally been observed (see, forexample, FIG. 1 in Prelec (infra, 1997)) that the dose distribution forions includes a significantly sharper maximum (the Bragg peak), and thations exhibit significantly less lateral scattering, than other particlessuch as electrons and neutrons and other forms of electromagneticradiation such as x-rays. Accordingly, due to the relativelywell-controlled dosing profile of accelerated ions, they operaterelatively efficiently to alter the structure of biomass material.Furthermore, as is apparent from FIG. 6 of Prelec (infra, 1997), heavierions (such as carbon ions) have even sharper dosing profiles thanlighter ions such as protons, and so the relative effectiveness of theseheavier ions at treating biomass material is even greater than forlighter ions.

In some embodiments, the average energy of the accelerated ions that areincident on biomass material is 1 MeV/u or more (e.g., 2, 3, 4, 5, 6, 7,8, 9, 10, 12, 15, 20, 30, 50, 100, 300, 500, 600, 800, or even 1000MeV/u or more).

In certain embodiments, the average energy of the accelerated ions is 10MeV or more (e.g., 20, 30, 50, 100, 200, 300, 400, 500, 600, 800, 1000,2000, 3000, 4000, or even 5000 MeV or more).

In certain embodiments, an average velocity of the accelerated ions is0.0005 c or more (e.g., 0.005 c or more, 0.05 c or more, 0.1 c or more,0.2 c or more, 0.3 c or more, 0.4 c or more, 0.5 c or more, 0.6 c ormore, 0.7 c or more, 0.8 c or more, 0.9 c or more), where c representsthe vacuum velocity of light. In general, for a given acceleratingpotential, lighter ions are accelerated to higher velocities thanheavier ions. For example, for a given accelerating potential, a maximumvelocity of a hydrogen ion may be about 0.05 c, while a maximum velocityof a carbon ion may be about 0.0005 c. These values are only exemplary;the velocity of the accelerated ions depends on the acceleratingpotential applied, the mode of operation of the accelerator, the numberof passes through the accelerating field, and other such parameters.

In some embodiments, an average ion current of the accelerated ions is10⁵ particles/s or more (eg., 10⁶, 10⁷, 10⁸, 10⁹, 10¹⁰, 10¹¹, 10¹²,10¹³, 10¹⁴, 10¹⁵, or even 10¹⁶ particles/s or more).

In some embodiments, a radiation dose delivered to biomass material froman ion beam is 5 Mrad or more (e.g., 10, 15, 20, 30, 40, 50, 60, 80, oreven 100 Mrad or more).

When a sample is exposed to an ion beam, energy is deposited in thesample according to an ion dose profile (also sometimes referred to as adepth-dose distribution). FIG. 2 shows a schematic diagram of arepresentative ion dose profile 2010 for a condensed-phase biomasssample. The vertical axis of ion dose profile 2010 in FIG. 2 shows therelative ion dose, plotted as a function of depth below a surface of thesample that is exposed to the ion beam, on the horizontal axis. FIG. 2also includes, for comparative purposes, an electron dose profile 2020,a gamma radiation dose profile 2030, and an x-ray dose profile 2040.

As shown in FIG. 2, both gamma radiation and x-ray radiation (andfurther, other types of electromagnetic radiation) are absorbed stronglyin a region adjacent to the surface of the sample, leading to thehighest energy doses being deposited near the sample surface. Gamma andx-ray radiation dose profiles 2030 and 2040 decrease approximatelyexponentially from the surface of the sample, as progressively fewerphotons are able to penetrate deeper into the sample to be absorbed.

Electron dose profile 2020 shows a build-up effect whereby, due to thepenetrating ability of Compton electrons, the deposited energy doseincreases in the vicinity of the exposed surface of the sample to amaximum deposited dose at a penetration depth of, typically, about 3-4cm in condensed media. Thereafter, the relative dose of deposited energydecreases relatively rapidly with increasing distance beneath the samplesurface.

Ion beams, in contrast, typically have dose profiles that are sometimesdescribed as being inverse with respect to the dose profiles ofelectrons and photons. As shown in FIG. 2, ion dose profile 2010includes a region 2012 in which a relatively constant energy dose isapplied to the sample. Thereafter, ion dose profile 2010 includes aregion 2014 referred to as the Bragg peak, which corresponds to aportion of the sample into which a comparatively larger fraction of theion beam's energy is deposited, followed by a region 2016 in which amuch smaller energy dose is deposited. The Bragg peak, which has a fullwidth at half maximum (FWHM) of δ, ensures that the dose profile forions differs significantly from the dose profiles for electrons andphotons of various wavelengths. As a result, exposing materials such asbiomass materials to ion beams can yield effects that are different fromthe effects produced by photons and electron beams.

Typically, the width δ of Bragg peak 2014 depends upon a number offactors, including the nature of the sample, the type of ions, and theaverage ion energy. One important factor that influences the width δ ofBragg peak 2014 is the distribution of energies in the incident ionbeam. In general, the narrower the distribution of energies in theincident ion beam, the narrower the width δ of Bragg peak 2014. As anexample, Bragg peak 2014 typically has a width of about 3 mm or less fora distribution of ion energies that has a FWHM of 1 keV or less. Thewidth δ of Bragg peak 2014 can be much less than 3 mm under theseconditions as well, e.g., 2.5 mm or less, 2.0 mm or less, 1.5 mm orless, 1.0 mm or less.

The position of Bragg peak 2014, indicated by γ in FIG. 2, depends upona number of factors including the average energy of the incident ionbeam. In general, for larger average ion beam energies, Bragg peak 2014will shift to larger depths in FIG. 2, because higher-energy ions havethe ability to penetrate more deeply into a material before most of theions' kinetic energy is lost via scattering events.

Various properties of one or more incident ion beams can be adjusted toexpose samples (e.g., biomass materials) to ion beam radiation, whichcan lead to de-polymerization and other chain-scission reactions in thesamples, reducing the molecular weight of the samples in a predictableand controlled manner. FIG. 3 shows a schematic diagram of an ion beamexposure system 2100. System 2100 includes an ion source 2110 thatgenerates an ion beam 2150. Optical elements 2120 (including, forexample, lenses, apertures, deflectors, and/or other electrostaticand/or magnetic elements for adjusting ion beam 2150) direct ion beam2150 to be incident on sample 2130, which has a thickness h in adirection normal to surface 2135 of sample 2130. In addition todirecting ion beam 2150, optical elements 2120 can be used to controlvarious properties of ion beam 2150, including collimation and focusingof ion beam 2150. Sample 2130 typically includes, for example, one ormore of the various types of biomass materials that are discussedherein. System 2100 also includes an electronic controller 2190 inelectrical communication with the various components of the system (andwith other components not shown in FIG. 3). Electronic controller 2190can control and/or adjust any of the system parameters disclosed herein,either fully automatically or in response to input from a humanoperator.

FIG. 3 also shows the ion dose profile that results from exposure ofsample 2130 to ion beam 2150. The position 2160 of the Bragg peak withinsample 2130 depends upon the average energy of ion beam 2150, the natureof the ions in ion beam 2150, the material from which sample 2130 isformed, and other factors.

In many applications of ion beams, such as ion therapy for tumoreradication, the relatively small width δ of Bragg peak 2014 isadvantageous, because it allows reasonably fine targeting of particulartissues within a patient undergoing therapy, and helps to reduce damagedue to exposure of nearby benign tissues.

However, when exposing biomass materials such as sample 2130 to ion beam2150, the relatively small width δ of Bragg peak 2014 can restrictthroughput. Typically, for example, the thickness h of sample 2130 islarger than the width δ of Bragg peak 2014. In some embodiments, h canbe substantially larger than 6 (e.g., larger by a factor of 5 or more,or 10 or more, or 20 or more, or 50 or more, or 100 or more, or evenmore).

To increase a thickness of sample 2130 in which a selected dose can bedelivered in a particular time interval, the energy distribution of ionbeam 2150 can be adjusted. Various methods can be used to adjust theenergy distribution of ion beam 2150. One such method is to employ oneor more removable scattering elements 2170 positioned in the path of ionbeam 2150, as shown in FIG. 3. Scattering element 2170 can be, forexample, a thin membrane formed of a metal material such as tungsten,tantalum, copper, and/or a polymer-based material such as Lucite®polymer.

Prior to passing through scattering element 2170, ion beam 2150 has anenergy distribution of width w, shown in FIG. 4A. When ion beam 2150passes through element(s) 2170, at least some of the ions in ion beam2150 undergo scattering events with atoms in element(s) 2170transferring a portion of their kinetic energy to the atoms ofelement(s) 2170. As a result, the energy distribution of ion beam 2150is broadened to a width b larger than w, as shown in FIG. 4B. Inparticular, the energy distribution of ion beam 2150 acquires a broaderlow-energy tail as a result of scattering in element(s) 2170.

FIG. 4C shows the effect of broadening the ion energy distribution ofion beam 2150 on the ion dose profiles in sample 2130. Ion dose profile2140 a is produced by exposing sample 2130 to ion beam 2150 having theion energy distribution shown in FIG. 4A. Ion dose profile 2140 aincludes a relatively narrow Bragg peak. As a result, the region ofsample 2130 in which a relatively high dose is deposited is small. Incontrast, by broadening the ion energy distribution of ion beam 2150 toyield the distribution shown in FIG. 4B, ion dose profile 2140 b isobtained in sample 2130 after exposing the sample to the broadeneddistribution of ion energies. As dose profile 2140 b shows, bybroadening the ion energy distribution, the region of sample 2130 inwhich a relatively high dose is deposited is increased relative to iondose profile 2140 a. By increasing the region of sample 2130 exposed toa relatively high dose, the throughput of the exposure process can beimproved.

In certain embodiments, the width b of the broadened energy distributioncan be larger than w by a factor of 1.1 or more (e.g., 1.2, 1.3, 1.4,1.5, 1.7, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, or even 10.0 or more).

Typically, the ion dose profile in sample 2130 produced by exposure ofthe sample to the broadened ion energy distribution shown in FIG. 4B hasa Bragg peak having a full width at half maximum (FWHM) of ε. As aresult of broadening the ion energy distribution, ε can be larger than δby a factor of 1.1 or more (e.g., 1.2 or more, 1.3 or more, 1.5 or more,1.7 or more, 2.0 or more, 2.5 or more, 3.0 or more, 4.0 or more, 5.0 ormore, 6.0 or more, 7.0 or more, 10.0 or more).

For sample 2130 of thickness h, after broadening the ion energydistribution of ion beam 2150 and exposing the sample to the ion beam, aratio of ε/h can be 1×10⁻⁶ or more (e.g., 1×10⁻⁵, 5×10⁻⁵, 1×10⁻⁴,5×10⁻⁴, 1×10⁻³, 5×10⁻³, 0.01, 0.05, 0.08, 0.1, or even 0.5 or more).

In certain embodiments, sample 2130 includes a plurality of particles(e.g., approximately spherical particles, and/or fibers, and/orfilaments, and/or other particle types). In general, the particles havea distribution of different sizes, with an average particle size r. Theion energy distribution of ion beam 2150 can be adjusted (e.g., viabroadening) based on the average particle size r of sample 2130 toimprove the efficiency of ion-based treatment of sample 2130. Forexample, ion beam 2150 can be adjusted so that a ratio of ε/r is 0.001or more (e.g., 0.005 or more, 0.01 or more, 0.05 or more, 0.1 or more,0.5 or more, 1.0 or more, 1.5 or more, 2.0 or more, 2.5 or more, 3.0 ormore, 3.5 or more, 4.0 or more, 5.0 or more, 6.0 or more, 8.0 or more,10 or more, 50 or more, 100 or more, 500 or more, 1000 or more, or evenmore).

In some embodiments, a scattering element 2170 can include multipledifferent scattering sub-elements that are configured to broaden thedistribution of ion energies in ion beam 2150 by different amounts. Forexample, FIG. 5 shows a multi-sub-element scattering element 2170 thatincludes sub-elements 2170 a-e. Each of sub-elements 2170 a-e broadensthe distribution of ion energies in ion beam 2150 to a different extent.During operation of system 2100, electronic controller 2190 can beconfigured to select an appropriate sub-element of scattering element2170 based on information such as the thickness h of sample 2130, thetype of ions in ion beam 2150, and the average ion energy in ion beam2150. The selection of an appropriate sub-element can be made in fullyautomated fashion, or based at least in part on input from a humanoperator. Selection of an appropriate sub-element is made by translatingscattering element 2170 in the direction shown by arrow 2175 to positiona selected sub-element in the path of ion beam 2150.

In certain embodiments, other devices can be used in addition to, or asan alternative to, scattering element(s) 2170. For example, in someembodiments, combinations of electric and or magnetic fields, producedby ion optical elements, can be used to broaden the ion energydistribution of ion beam 2150. Ion beam 2150 can pass through a firstfield configured to spatially disperse ions in the ion beam. Then thespatially dispersed ions can pass through a second field that iswell-localized spatially, and which selectively retards only a portionof the spatially dispersed ions. The ions then pass through a thirdfield that spatially re-assembles all of the ions into a collimatedbeam, which is then directed onto the surface of sample 2130. Typically,the ion optical elements used to generate the fields that adjust the ionenergy distribution are controlled by electronic controller 2190. Byapplying spatially localized fields selectively, a high degree ofcontrol over the modified ion energy distribution is possible, includingthe generation of ion energy distributions having complicated profiles(e.g., multiple lobes). For example, in some embodiments, by applying alocalized field that accelerates a portion of the spatially dispersedion distribution, the ion energy distribution shown in FIG. 4A can bebroadened on the high-energy side of the distribution maximum.

The information used by electronic controller 2190 to adjust the ionenergy distribution of ion beam 2150 can include the thickness h ofsample 2130, as discussed above. In some embodiments, electroniccontroller 2190 can use information about the expected ion dose profilein sample 2130 to adjust the ion energy distribution of ion beam 2150.Information about the expected ion dose profile can be obtained from adatabase, for example, that includes measurements of ion dose profilesacquired from literature sources and/or from calibration experimentsperformed on representative samples of the material from which sample2130 is formed. Alternatively, or in addition, information about theexpected ion dose profile can be determined from a mathematical model ofion interactions in sample 2130 (e.g., an ion scattering model).

In certain embodiments, the information about the expected ion doseprofile can include information about the FWHM of the Bragg peak in theexpected ion dose profile. The FWHM of the Bragg peak can be determinedfrom measurements of ion dose profiles and/or from one or moremathematical models of ion scattering in the sample. Adjustments of theion energy distribution of ion beam 2150 can be performed to reduce adifference between the thickness h of sample 2130 and the FWHM of theBragg peak. In some embodiments, for example, a difference between h andthe full width at half maximum of the Bragg peak is 20 cm or less (e.g.,18, 16, 14, 12, 10, 8, 6 cm, 5, 4, 3, 2, 1, 0.5, 0.1, 0.05, 0.01, 0.001,0.0001, or even 0.00001 cm or less, or even zero).

In some embodiments, the ion beam exposure system can adjust thedistribution of ion energies in ion beam 2150 in other ways. Forexample, the ion beam exposure system can be configured to filter theion beam by removing ions from ion beam 2150 that have energies below aselected energy threshold and/or above a selected energy threshold. FIG.6 shows an ion beam exposure system 2200 that includes an ion filter2210 discussed in more detail below. The other components of system 2200are similar to the components of system 2100, and will not be furtherdiscussed.

FIG. 7A shows an ion energy distribution corresponding to ion beam 2150produced by ion source 2110. Ion beam 2150, with an energy distributionas shown in FIG. 7A, enters ion filter 2210 where the energydistribution of ion beam 2150 is adjusted by filtering out certain ionsfrom the ion beam. For example, in some embodiments, ion filter 2210 canbe configured to remove ions from ion beam 2150 that have an energysmaller than a selected energy threshold. In FIG. 7A, the selectedenergy threshold is the position E₀ of the peak in the ion energydistribution, although more generally, any energy threshold can beselected. By filtering out all (or even just a large fraction of) ionshaving an energy less than E₀, the ion energy distribution for ion beam2150 is as shown in FIG. 7B.

In contrast, in some embodiments, ion filter 2210 can be configured toremove ions from ion beam 2150 that have an energy larger than aselected energy threshold (when ion filter 2210 is implemented as ahemispherical analyzer, for example). For example, the selected energythreshold can correspond to the position E₀ of the peak in the ionenergy distribution, although more generally, any energy threshold canbe selected. By removing all (or even a large fraction of) ions from ionbeam 2150 having an energy more than E₀, the ion energy distribution forion beam 2150 is as shown in FIG. 7C.

In certain embodiments, sample 2130 can be exposed directly to afiltered ion beam 2150. By filtering the ion beam to achieve a narrowerion energy distribution, for example, the ion dose profile in sample2130 is sharper following sample exposure than it would otherwise havebeen without filtering ion beam 2150. As a result, the width of theBragg peak in sample 2130 is smaller relative to the Bragg peak widthfor an unfiltered ion beam. By exposing sample 2130 to a narrowerdistribution of incident ion energies, more refined control over theposition of ion beam 2150 can be achieved; this level of ion exposurecontrol can be useful when exposing various types of delicate samplematerials.

Alternatively, the filtered ion beam can then be passed through one ormore scattering elements and/or other devices to increase the width ofthe distribution of ion energies. This two-step approach to modifyingthe ion energy distribution—a first filtering step, followed by a secondbroadening step—can be used to produce ion energy distributions that aretailored for specific applications (e.g., specific to certain ion typesand/or certain materials and/or certain pre-treatment conditions) thatmay not be achievable using a simpler one-step energy distributionbroadening procedure.

As an example, by first filtering ion beam 2150, and then passing thefiltered ion beam through one or more scattering elements 2170, theshape of the ion energy distribution can be made more Gaussian thanwould otherwise be possible using only a scattering step instead of thetwo-step procedure.

Ion filter 2210 can include one or more of a variety of differentdevices for removing ions from ion beam 2150. For example, in someembodiments, ion filter 2210 includes a hemispherical analyzer andaperture filter. The hemispherical analyzer includes a magnetic fieldsource that disperses the ions of ion beam 2150 according to theirkinetic energies. The aperture filter is then positioned in the path ofthe dispersed ion beam 2150 to permit only ions having a particularrange of energies to pass through the aperture.

In certain embodiments, other devices can be used to filter ion beam2150. For example, absorbing elements (e.g., elements configured toabsorb incident ions having energies smaller than a selected energythreshold can be used to filter ion beam 2150. Suitable absorbingelements include metal foils, for example.

In some embodiments, ion beam 2150 (and in particular, the Bragg peak inan expected ion dose profile produced following exposure of sample 2130to ion beam 2150) can be swept through sample 2130 to deliver selectedradiation doses to various portions of the sample. In general, theposition of the Bragg peak in sample 2130 can be selected by adjustingthe average energy of ion beam 2150 (the average energy of ion beam 2150typically corresponds to the maximum in the ion energy distribution).Ion source 2110, under the control of electronic controller 2190, canadjust the average energy of ion beam 2150 by changing an extractionvoltage applied to accelerate ions in the ion source.

FIG. 8 is a schematic diagram that shows how the Bragg peak of an iondose profile in sample 2130 can be swept through the sample. As a firststep, ion exposure system 2100 is configured to produce a first ion beamwith a selected average ion energy corresponding to a particularextraction voltage applied in ion source 2110. When sample 2130 isexposed to the first ion beam, ion dose profile 2010 a results in thesample, with the Bragg peak at position 2230 a. Following exposure, theextraction voltage in ion source 2110 is adjusted to produce a secondion beam with a different average ion energy. When sample 2130 isexposed to the second ion beam, ion dose profile 2010 b results in thesample. By further repeating the adjusting of the extraction voltage inion source 2110 to produce additional beams with different average ionenergies (and, therefore, different ion dose profiles, e.g., ion doseprofile 2010 c), and exposing sample 2130 to the additional beams, theBragg peak of the ion dose profile can be swept through sample 2130 inthe direction shown by arrow 2220, for example. More generally, however,by changing the extraction voltage in ion source 2110, the position ofthe Bragg peak in sample 2130 can be selected as desired, permittingdelivery of large doses to selected regions of sample 2130 in anysequence.

In general, other properties of ion beam 2150 can also be adjusted inaddition to, or as an alternative to, adjusting the average ion energyof the ion beam. For example, in some embodiments, the divergence angleof ion beam 2150 at the surface of sample 2130 can be adjusted tocontrol the ion dose profile in sample 2130. Generally, by increasingthe divergence angle of ion beam 2150 at the surface of sample 2130, thefull width at half maximum of the Bragg peak in sample 2130 can beincreased. Thus, in certain embodiments, the average energy of the ionbeam can be maintained, but the ion dose profile in thematerial—including the position of the Bragg peak—can be changed byadjusting the ion beam's divergence angle.

The divergence angle can be adjusted automatically or by operatorcontrol by electronic controller 2190. Typically optical elements 2120include one or more ion beam steering elements such as quadrupole and/oroctopole deflectors. By adjusting potentials applied to the variouselectrodes of such deflectors, the divergence angle (and the angle ofincidence) of ion beam 2150 at the surface of sample 2130 can beadjusted.

In some embodiments—unlike in other applications of ion beams such assurgical intervention—it can be advantageous to use ion beams withrelatively large divergence angles, to ensure that the Bragg peakpositioned in sample 2130 covers a suitable fraction of the thickness ofsample 2130. For example, in certain embodiments, sample 2130 can beexposed to an ion beam having a divergence angle of 2 degrees or more(e.g., 5, 10, 15, 20, 30, 40, or even 50 degrees or more).

In some embodiments, both an ion beam current of ion beam 2150 and theaverage ion energy of ion beam 2150 can be adjusted to deliver arelatively constant dose as a function of thickness h of sample 2130.For example, if sample 2130 is exposed according to the sequential iondose profiles 2010 a, 2010 b, and 2010 c in FIG. 8, the net ion doseprofile in sample 2130 corresponds to the sum of profiles 2010 a-c,which is shown in FIG. 9A. Based on the net ion dose profile of FIG. 9A,it is evident that certain regions of sample 2130 receive larger netdoses than other regions of sample 2130.

The differences in net dose can be reduced by adjusting the ion beamcurrent of ion beam 2150 together with adjustments of the average ionenergy. The ion beam current can be adjusted in ion source 2110 underthe control of electronic controller 2190. For example, to reduce thedifference in the net dose delivered to sample 2130 when the Bragg peakis swept through sample 2130 in the direction indicated by arrow 2220 inFIG. 8, the ion beam current can be successively reduced for eachsuccessive reduction in ion beam energy. Three ion dose profiles, eachcorresponding to successive decreases in both average ion energy and ioncurrent in ion beam 2150, are shown as profiles 2010 d-f, respectively,in FIG. 9B. The net ion dose profile in sample 2130 that results fromthese three sequential exposures is shown in FIG. 9C. The net ion doseprofile shows significantly reduced variation as a function of positionin sample 2130 relative to the net ion dose profile of FIG. 9A.

By carefully controlling the average energy and ion current of ion beam2150, variations in net relative ion dose through the thickness ofsample 2130 following exposure of the sample to ion beam 2150 can berelatively small. For example, a difference between a maximum netrelative ion dose and a minimum net relative ion dose in sample 2130following multiple exposures to ion beam 2150 can be 0.2 or less (e.g.,0.15, 0.1, 0.05, 0.04, 0.03, 0.02, 0.01 or even 0.005 or less).

By controlling the average energy and ion current of ion beam 2150, eachportion of the exposed sample can receive a net dose of between 0.001Mrad and 100 Mrad following multiple exposures to the ion beam (e.g.,between 0.005 Mrad and 50 Mrad, between 0.01 Mrad and 50 Mrad, between0.05 Mrad and 30 Mrad, between 0.1 Mrad and 20 Mrad, between 0.5 Mradand 20 Mrad, or between 1 Mrad and 10 Mrad).

In some embodiments, sample 2130 can be exposed to different types ofions. Sample 2130 can be sequentially exposed to only one type of ion ata time, or the exposure of sample 2130 can include exposing sample 2130to one or more ion beams that include two or more different types ofions. Different types of ions produce different ion dose profiles in anexposed material, and, by exposing a sample to different types of ions,a particular net ion dose profile in the sample can be realized. FIG.10A shows a schematic diagram of three different ion dose profiles 2010g-i that result from exposing a sample 2130 to three different types ofions. Ion dose profiles 2010 g-i can be produced via sequential exposureof the sample to each one of the different types of ions, or viaconcurrent exposure of the sample to two or even all three of thedifferent types of ions. The net ion dose profile in sample 2130 thatresults from exposure to the three different types of ions is shown inFIG. 10B. Variations in the net ion dose profile as a function ofthickness of the sample are reduced relative to any one of theindividual ion dose profiles shown in FIG. 10A.

In some embodiments, the different types of ions can include ions ofdifferent atomic composition. For example, the different types of ionscan include protons, carbon ions, oxygen ions, hydride ions, nitrogenions, chlorine ions, fluorine ions, argon ions, neon ions, krypton ions,and various types of metal ions such as sodium ions, calcium ions, andlithium ions. Generally, any of these different types of ions can beused to treat sample 2130, and each will produce a different ion doseprofile in a sample. In certain embodiments, ions can be generated fromcommonly available gases such as air. When air is used as a source gas,many different types of ions can be generated. The various differenttypes of ions can be separated from one another prior to exposing sample2130, or sample 2130 can be exposed to multiple different types of ionsgenerated from a source gas such as air.

In some embodiments, the different types of ions can include ions havingdifferent charges. For example, the different types of ions can includevarious positive and/or negative ions. Further, the different types ofions can include ions having single and/or multiple charges. In general,positive and negative ions of the same chemical species can producedifferent ion dose profiles in a particular sample, and ions of the samechemical species that have different charge magnitudes (e.g.,singly-charged, doubly-charged, triply-charged, quadruply-charged) canproduce different ion dose profiles in a particular sample. By exposinga sample to multiple different types of ions, the change in the sample,e.g., sample breakdown (e.g., depolymerization, chain scission, and/ormolecular weight reduction), functionalization, or other structuralchange, can be carefully and selectively controlled.

In some embodiments, the ion beam exposure system can adjust thecomposition of the ion beam based on the sample material. For example,certain types of sample, such as cellulosic biomass, include a largeconcentration of hydroxyl moieties. Accordingly, the effectivepenetration depth of certain types of ions—particularly protons—in suchmaterials can be considerably larger than would otherwise be expectedbased on ion energy alone. Site-to-site proton hopping and other similaratomic excursions can significantly increase the mobility of such ionsin the sample, effectively increasing the penetration depth of theincident ions. Further, the increased mobility of the ions in the samplecan lead to a broadening of the Bragg peak. The ion beam exposure systemcan be configured to select particular types of ions for exposure ofcertain samples, accounting for the chemical and structural features ofthe sample. Further, the ion beam exposure system can be configured totake into account the expected interactions between the ion beam and thematerial when determining how to modify other parameters of the ion beamsuch as the distribution of ion energies therein.

An important aspect of the ion beam systems and methods disclosed hereinis that the disclosed systems and methods enable exposure of biomass toions in the presence of one or more additional fluids (e.g., gasesand/or liquids). Typically, for example, when a material is exposed toan ion beam, the exposure occurs in a reduced pressure environment suchas a vacuum chamber. The reduced pressure environment is used to reduceor prevent contamination of the exposed material, and also to reduce orprevent scattering of the ion beam by gas molecules. Unfortunately, ionbeam exposure of materials in closed environments such as a vacuumchamber greatly restricts potential throughput for high volume materialprocessing, however.

In the systems and methods disclosed herein, it has been recognized thatexposure of biomass to an ion beam in the presence of one or moreadditional fluids can increase the efficiency of the biomass treatment.Additionally, exposure of biomass to an ion beam in an open environment(e.g., in air at normal atmospheric pressure) provides for much higherthroughput than would otherwise be possible in a reduced pressureenvironment.

As discussed above, in some embodiments, biomass is exposed to an ionbeam in the presence of a fluid such as air. Ions accelerated in any oneor more of the types of accelerators disclosed herein (or another typeof accelerator) are coupled out of the accelerator via an output port(e.g., a thin membrane such as a metal foil), pass through a volume ofspace occupied by the fluid, and are then incident on the biomassmaterial. In addition to directly treating the biomass, some of the ionsgenerate additional chemical species by interacting with fluid particles(e.g., ions and/or radicals generated from various constituents of air).These generated chemical species can also interact with the biomass, andcan act as initiators for a variety of different chemical bond-breakingreactions in the biomass (e.g., depolymerization and otherchain-scission reactions).

In certain embodiments, additional fluids can be selectively introducedinto the path of an ion beam before the ion beam is incident on thebiomass. As discussed above, reactions between the ions and theparticles of the introduced fluids can generate additional chemicalspecies which react with the biomass and can assist in reducing themolecular weight of the biomass, and/or otherwise selectively alteringcertain properties of the biomass. The one or more additional fluids canbe directed into the path of the ion beam from a supply tube, forexample. The direction (i.e., fluid vector) and flow rate of thefluid(s) that is/are introduced can be selected according to a desiredexposure rate and/or direction to control the efficiency of the overallbiomass treatment, including effects that result from both ion-basedtreatment and effects that are due to the interaction of dynamicallygenerated species from the introduced fluid with the biomass. Inaddition to air, exemplary fluids that can be introduced into the ionbeam include oxygen, nitrogen, one or more noble gases, one or morehalogens, and hydrogen.

In some embodiments, ion beams that include more that one different typeof ions can be used to treat biomass. Beams that include multipledifferent types of ions can be generated by combining two or moredifferent beams, each formed of one type of ion. Alternatively, or inaddition, in certain embodiments, ion beams that include multipledifferent types of ions can be generated by introducing a multicomponentsupply gas into an ion source and/or accelerator. For example, amulticomponent gas such as air can be used to generate an ion beamhaving different types of ions, including nitrogen ions, oxygen ions,argon ions, carbon ions, and other types of ions. Other multicomponentmaterials (e.g., gases, liquids, and solids) can be used to generate ionbeams having different compositions. Filtering elements (e.g.,hemispherical electrostatic filters) can be used to filter out certainionic constituents and/or neutral species to selectively produce an ionbeam having a particular composition, which can then be used to treatbiomass. By using air as a source for producing ion beams for biomasstreatment, the operating costs of a treatment system can be reducedrelative to systems that rely on pure materials, for example.

Certain types of biomass materials may be particularly amenable totreatment with multiple different types of ions and/or multipledifferent processing methods. For example, cellulosic materialstypically include crystalline polymeric cellulose chains which arecross-linked by amorphous hemicellulose fraction. The cellulose andhemicellulose is embedded within an amorphous lignin matrix. Separationof the cellulose fraction from the lignin and the hemicellulose usingconventional methods is difficult and can be energy-intensive.

However, cellulosic biomass can be treated with multiple different typesof ions to break down and separate the various components therein forfurther processing. In particular, the chemical properties of varioustypes of ionic species can be used to process cellulosic biomass (andother types of biomass) to selectively degrade and separate thecomponents thereof. For example, positively charged ions—and inparticular, protons—act as acids when exposed to biomass material.Conversely, negatively charged ions, particularly hydride ions, act asbases when exposed to biomass material. As a result, the chemicalproperties of these species can be used to target specific components oftreated biomass.

When treating lignocellulosic biomass, for example, the lignin matrixtypically decomposes in the presence of basic reagents. Accordingly, byfirst treating cellulosic biomass with basic ions such as hydride ions(or electrons) from an ion (electron) beam, the lignin fraction can bepreferentially degraded and separated from the cellullose andhemicellulose fractions. Cellulose is relatively unaffected by such anion treatment, as cellullose is typically stable in the presence ofbasic agents.

In addition to negative ion treatment (or as an alternative to negativeion treatment), the lignocellulosic biomass can be treated with one ormore basic agents in solution to assist in separating the lignin. Forexample, treatment of the lignocellulosic biomass with a sodiumbicarbonate solution can degrade and/or solubilize the lignin, enablingseparation of the solvated and/or suspended lignin from the celluloseand hemicellulose fractions.

Negative ion treatment with an ion beam may also assist in separatinghemicellulose, which is also chemically sensitive to basic reagents.Depending upon the particular structure of the cellulosic biomass, morethan treatment with negative ions may be used (and/or may be necessary)to effectively separate the hemicellulose fraction from the cellulosefraction. In addition, more that one type of ion can be used to separatethe hemicellulose. For example, a relatively less basic ion beam such asan oxygen ion beam can be used to treat cellulosic biomass to degradeand/or remove the lignin fraction. Then, a stronger basic ion beam suchas a hydride ion beam can be used to degrade and separate thehemicellulose from the cellulose. The cellulosic fraction remainslargely unchanged as a result of exposure to two different types ofbasic ions.

However, the cellulose fraction decomposes in the presence of acidicagents. Accordingly, a further processing step can include exposing thecellulose fraction to one or more acidic ions such as protons from anion beam, to assist in depolymerizing and/or degrading the cellulosefraction.

Each of the ion beam pretreatments and methods disclosed herein can beused in combination with other processing steps. For example, separationsteps (including introducing a solvent such as water) can be used towash away particular fractions of the cellulosic biomass as they aredegraded. Additional chemical agents can be added to assist inseparating the various components. For example, it has been observedthat lignin that is separated from the cellulose and hemicellulosefractions can be suspended in a washing solution. However, the lignincan readily re-deposit from the solution onto the cellulose andhemicellulose fractions. To avoid re-deposition of the lignin, thesuspension can be gently heated to ensure that the lignin remains belowits glass transition temperature, and therefore remains fluid. Bymaintaining the lignin below its glass transition temperature, thelignin can be more readily washed out of cellulosic biomass. In general,heating of the suspension is carefully controlled to avoid thermaldegradation of the sugars in the cellulosic fraction.

In addition, other treatment steps can be used to remove lignin fromcellulose and hemicellulose. For example, in certain embodiments,lignocellulosic biomass can first be treated with relatively heavy ions(e.g., carbon ions, oxygen ions) to degrade lignin, and the celluloseand hemicellulose can then be treated with relatively light ions (e.g.,protons, helium ions) and/or electrons to cause degradation of thecellulose and/or hemicellulose.

In some embodiments, one or more functionalizing agents can be added tothe suspension containing the lignin to enhance the solubility of ligninin solution, thereby discouraging re-deposition on the cellulose andhemicellulose fractions. For example, agents such as ammonia gas and/orvarious types of alcohols can be used (to introduce amino andhydroxyl/alkoxy groups, respectively) to functionalize the lignin.

In certain embodiments, structural agents can be added to the ligninsuspension to prevent re-deposition of the lignin onto the cellulose andhemicellulose fractions. Typically, when lignin forms a matrixsurrounding cellulose and/or hemicellulose, the lignin adopts a heavilyfolded structure which permits relatively extensive van der Waalsinteractions with cellulose and hemicellulose. In contrast, when ligninis separated from cellulose and hemicellulose, the lignin adopts a moreopen, unfolded structure. By adding one or more agents that assist inpreventing lignin re-folding to the lignin suspension, re-association ofthe lignin with cellulose and hemicellulose can be discouraged, and thelignin can be more effectively removed via washing, for example.

In some embodiments, no chemicals, e.g., no swelling agents, are addedto the biomass prior to irradiation. For example, alkaline substances(such as sodium hydroxide, potassium hydroxide, lithium hydroxide andammonium hydroxides), acidifying agents (such as mineral acids (e.g.,sulfuric acid, hydrochloric acid and phosphoric acid)), salts, such aszinc chloride, calcium carbonate, sodium carbonate,benzyltrimethylammonium sulfate, or basic organic amines, such asethylene diamine, may or may not be added prior to irradiation or otherprocessing. In some cases, no additional water is added. For example,the biomass prior to processing can have less than 0.5 percent by weightadded chemicals, e.g., less than 0.4, 0.25, 0.15 or 0.1 percent byweight added chemicals. In some instances, the biomass has no more thana trace, e.g., less than 0.05 percent by weight added chemicals, priorto irradiation. In other instances, the biomass prior to irradiation hassubstantially no added chemicals or swelling agents. Avoiding the use ofsuch chemicals can also be extended throughout processing, e.g., at alltimes prior to fermentation, or at all times.

The various ion beam pretreatment methods disclosed herein can be usedcooperatively with other pretreatment techniques such as sonication,electron beam irradiation, electromagnetic irradiation, steam explosion,chemical methods, and biological methods. Ion beam techniques providesignificant advantages, including the ability to perform ion beamexposure of dry samples, to deliver large radiation doses to samples inshort periods of time for high throughput applications, and to exerciserelatively precise control over exposure conditions.

Quenching and Controlled Functionalization

After treatment with ionizing radiation, the materials described hereinbecome ionized; that is, they include radicals at levels that aredetectable with an electron spin resonance spectrometer. The currentpractical limit of detection of the radicals is about 10¹⁴ spins at roomtemperature. After ionization, any material that has been ionized can bequenched to reduce the level of radicals in the ionized material, e.g.,such that the radicals are no longer detectable with the electron spinresonance spectrometer. For example, the radicals can be quenched by theapplication of a sufficient pressure to the material and/or by utilizinga fluid in contact with the ionized material, such as a gas or liquid,that reacts with (quenches) the radicals. The use of a gas or liquid toat least aid in the quenching of the radicals also allows the operatorto control functionalization of the ionized material with a desiredamount and kind of functional groups, such as carboxylic acid groups,enol groups, aldehyde groups, nitro groups, nitrile groups, aminogroups, alkyl amino groups, alkyl groups, chloroalkyl groups orchlorofluoroalkyl groups. In some instances, such quenching can improvethe stability of some of the ionized materials. For example, quenchingcan improve the resistance of the material to oxidation.Functionalization by quenching can also improve the solubility of thematerials described herein, can improve the thermal stability of amaterial, and can improve material utilization by variousmicroorganisms. For example, the functional groups imparted to a biomassmaterial by quenching can act as receptor sites for attachment bymicroorganisms, e.g., to enhance cellulose hydrolysis by variousmicroorganisms.

Thus, a molecular and/or a supramolecular structure of a feedstock canbe changed by pretreating the feedstock with ionizing radiation, such aswith electrons or ions of sufficient energy to ionize the feedstock, toprovide a first level of radicals. If an ionized feedstock remains inthe atmosphere, it will be oxidized, for example causing carboxylic acidgroups to be generated by reacting with the atmospheric oxygen. In someinstances with some materials, such oxidation is desired because it canaid in further breakdown in molecular weight, for example of acarbohydrate-containing biomass, and the oxidation groups, e.g.,carboxylic acid groups, can be helpful for solubility and microorganismutilization. However, since the radicals can “live” for some time afterirradiation, e.g., longer than 1 day, 5 days, 30 days, 3 months, 6months or even longer than 1 year, material properties can continue tochange over time, which in some instances, can be undesirable. Detectingradicals in irradiated samples by electron spin resonance spectroscopyand radical lifetimes in such samples is discussed in Bartolotta et al.,Physics in Medicine and Biology, 46 (2001), 461-471 and in Bartolotta etal., Radiation Protection Dosimetry, Vol. 84, Nos. 1-4, pp. 293-296(1999). The ionized material can be quenched to functionalize and/or tostabilize it. At any point, e.g., when the material is “alive”,“partially alive” or fully quenched, the material can be converted intoa product, e.g., a fuel, a food, or a composite.

In some embodiments, the quenching includes an application of pressure,such as by mechanically deforming the material, e.g., directlymechanically compressing the material in one, two, or three dimensions,or applying pressure to a fluid in which the material is immersed, e.g.,isostatic pressing. In such instances, the deformation of the materialitself brings radicals, which are often trapped in crystalline domains,in sufficient proximity so that the radicals can recombine, or reactwith another group. In some instances, the pressure is applied togetherwith the application of heat, such as a sufficient quantity of heat toelevate the temperature of the material to above a melting point orsoftening point of a component of the material, such as lignin,cellulose or hemicellulose in the case of a biomass material. Heat canimprove molecular mobility in the material, which can aid in thequenching of the radicals. When pressure is utilized to quench, thepressure can be greater than about 1000 psi, such as greater than about1250 psi, 1450 psi, 3625 psi, 5075 psi, 7250 psi, 10000 psi or evengreater than 15000 psi.

In some embodiments, quenching includes contacting the material with afluid, such as a liquid or gas, e.g., a gas capable of reacting with theradicals, such as acetylene or a mixture of acetylene in nitrogen,ethylene, chlorinated ethylenes or chlorofluoroethylenes, propylene ormixtures of these gases. In other particular embodiments, quenchingincludes contacting the material, e.g., biomass, with a liquid, e.g., aliquid soluble in, or at least capable of penetrating into the biomassand reacting with the radicals, such as a diene, such as1,5-cyclooctadiene. In some specific embodiments, the quenching includescontacting the biomass with an antioxidant, such as Vitamin E. Ifdesired, the feedstock can include an antioxidant dispersed therein, andthe quenching can come from contacting the antioxidant dispersed in thefeedstock with the radicals.

Other methods for quenching are possible. For example, any method forquenching radicals in polymeric materials described in Muratoglu et al.,U.S. Patent Application Publication No. 2008/0067724 and Muratoglu etal., U.S. Pat. No. 7,166,650, can be utilized for quenching any ionizedmaterial described herein. Furthermore any quenching agent (described asa “sensitizing agent” in the above-noted Muratoglu disclosures) and/orany antioxidant described in either Muratoglu reference can be utilizedto quench any ionized material.

Functionalization can be enhanced by utilizing heavy charged ions, suchas any of the heavier ions described herein. For example, if it isdesired to enhance oxidation, charged oxygen ions can be utilized forthe irradiation. If nitrogen functional groups are desired, nitrogenions or ions that includes nitrogen can be utilized. Likewise, if sulfuror phosphorus groups are desired, sulfur or phosphorus ions can be usedin the irradiation.

In some embodiments, after quenching any of the quenched materialsdescribed herein can be further treated with one or more of radiation,such as ionizing or non-ionizing radiation, sonication, pyrolysis, andoxidation for additional molecular and/or supramolecular structurechange.

In particular embodiments, functionalized materials described herein aretreated with an acid, base, nucleophile or Lewis acid for additionalmolecular and/or supramolecular structure change, such as additionalmolecular weight breakdown. Examples of acids include organic acids,such as acetic acid and mineral acids, such as hydrochloric, sulfuricand/or nitric acid. Examples of bases include strong mineral bases, suchas a source of hydroxide ion, basic ions, such as fluoride ion, orweaker organic bases, such as amines. Even water and sodium bicarbonate,e.g., when dissolved in water, can effect molecular and/orsupramolecular structure change, such as additional molecular weightbreakdown.

The functionalized materials can be used as substrate materials toimmobilize microorganisms and/or enzymes during bioprocessing, forexample as described in U.S. Provisional Application Ser. Nos.61/180,032 and 61/180,019, the disclosures of which are incorporatedherein by reference.

Other embodiments are within the scope of the following claims. Forexample, non-biomass materials and mixtures of biomass materials andnon-biomass materials can be processed using the methods describedherein. Examples of non-biomass materials that can be processed includehydrocarbon-containing materials such as oil sands, oil shale, tarsands, bitumen, coal, and other such mixtures of hydrocarbons andnon-hydrocarbon materials. Many other biomass and non-biomass materialscan be processed using the methods described herein, including peat,lignin, pre-coal, and petrified and/or carbonized materials.

What is claimed is:
 1. A method of changing a molecular structure of alignocellulosic material, the method comprising: producing an ion beamcomprising ions having a first distribution of ion energies having afull width at half maximum of W; adjusting the energies of at least someof the ions based on a thickness of the lignocellulosic material toproduce an adjusted ion beam in which the ions have a seconddistribution of ion energies having a full width at half maximum of morethan W; and exposing the lignocellulosic material to the adjusted ionbeam as the lignocellulosic material moves past the adjusted ion beam tocause chain scission of the lignocellulosic material.
 2. The method ofclaim 1, wherein the full width at half maximum of the seconddistribution is larger than W by a factor of 2.0 or more.
 3. The methodof claim 1, wherein the full width at half maximum of the seconddistribution is larger than W by a factor of 4.0 or more.
 4. The methodof claim 1, wherein adjusting the energies of at least some of the ionscomprises directing the ions to pass through a scattering element. 5.The method of claim 1, wherein adjusting the energies of at least someof the ions comprises directing the ions to pass through a hemisphericalanalyzer.
 6. The method of claim 1, wherein the adjusted ion beam passesthrough a fluid prior to being incident on the lignocellulosic material.7. The method of claim 6, wherein the fluid is air at a pressure of 0.5atmospheres or more.
 8. The method of claim 1, wherein the ion beamcomprises two or more different types of ions.
 9. The method of claim 8,wherein the two or more different types of ions comprise hydrogen ionsand carbon ions.
 10. The method of claim 8, wherein the two or moredifferent types of ions comprise hydrogen ions and oxygen ions.
 11. Themethod of claim 1 wherein the lignocellulosic material is not wettedwith a liquid prior to irradiation.
 12. A method of changing a molecularstructure of a lignocellulosic material, the method comprising:producing an ion beam comprising a distribution of ion energies having afull width at half maximum of W; directing the ion beam to pass througha scattering element configured to increase the full width at halfmaximum of the distribution of ion energies to a value larger than W;and exposing the lignocellulosic material to the ion beam downstream ofthe scattering element as the lignocellulosic material moves past theion beam to cause chain scission of the lignocellulosic material.
 13. Amethod of changing a molecular structure of a lignocellulosic material,the method comprising: producing an ion beam having a distribution ofion energies, the distribution having a most probable energy E;filtering the ion beam to remove at least some ions having an energyless than E from the ion beam; and exposing the lignocellulosic materialto the filtered ion beam as the lignocellulosic material moves past thefiltered ion beam to cause chain scission of the lignocellulosicmaterial.
 14. The method of claim 13, wherein filtering the ion beamcomprises directing the ion beam to pass through a metal foil.
 15. Themethod of claim 13, wherein filtering the ion beam comprises directingthe ion beam to pass through a hemispherical analyzer.
 16. A method ofchanging a molecular structure of a lignocellulosic material, the methodcomprising: producing an ion beam having a distribution of ion energies;adjusting the distribution of ion energies based on a full width at halfmaximum (FWHM) of a Bragg peak of an expected ion dose profile in thelignocellulosic material to produce an adjusted ion beam; and exposingthe lignocellulosic material to the adjusted ion beam as the materialmoves past the adjusted ion beam to cause chain scission of thelignocellulosic material, wherein the adjusting comprises increasing theFWHM enough to reduce a difference between a thickness of thelignocellulosic material and the FWHM.
 17. The method of claim 16,wherein the adjusting comprises directing the ion beam to pass through ascattering element.
 18. The method of claim 16, wherein, following theadjusting, the difference between the thickness of the biomass materialand the FWHM is 0.01 centimeter or less.
 19. A method of changing amolecular structure of a lignocellulosic material, the methodcomprising: producing a first ion beam from an ion source, the first ionbeam having a first average ion energy; exposing the lignocellulosicmaterial to the first ion beam as the lignocellulosic material movespast the first ion beam; adjusting the ion source to produce a secondion beam having a second average ion energy different from the firstaverage ion energy; and exposing the lignocellulosic material to thesecond ion beam as the lignocellulosic material moves past the secondion beam; wherein exposing the steps cause chain scission of thelignocellulosic material.
 20. The method of claim 19 wherein the firstion beam has a first average ion energy corresponding to a firstposition of a Bragg peak in an expected ion dose profile of the biomassmaterial and the second ion beam has a second average ion energycorresponding to a second position of the Bragg peak different from thefirst position.
 21. A method of changing a molecular structure of alignocellulosic material, the method comprising: producing an ion beamfrom an ion source, the ion beam comprising a first type of ions and asecond type of ions different from the first type of ions, the first andsecond type of ions being from different atomic elements; and exposingthe lignocellulosic material to the ion beam as the lignocellulosicmaterial moves past the ion beam to cause chain scission of thelignocellulosic material.
 22. A method of changing a molecular structureof a lignocellulosic material, the method comprising: producing a ionbeam; and exposing the lignocellulosic material to the ion beam at anincident surface of the lignocellulosic material as the lignocellulosicmaterial moves past the ion beam to cause chain scission of thelignocellulosic material; wherein the ion beam has a divergence angle of10 degrees or more at the incident surface of the lignocellulosicmaterial.
 23. The method of claim 22, wherein the divergence angle is 20degrees or more.
 24. A method of changing a molecular structure of alignocellulosic material, the method comprising: adjusting an ion sourceto produce an ion beam having an average ion current and an average ionenergy; and exposing the lignocellulosic material to the ion beam as thematerial moves past the ion beam to cause chain scission of thelignocellulosic material, wherein the ion source is adjusted based on anexpected ion dose profile in the lignocellulosic material and whereinthe lignocellulosic material receives a radiation dose of between 0.01Mrad and 50 Mrad as a result of exposure to the ion beam.
 25. The methodof claim 24, wherein the lignocellulosic material receives a radiationdose of between 0.1 Mrad and 20 Mrad as a result of exposure to the ionbeam.
 26. The method of claim 24, further comprising exposing thelignocellulosic material to a plurality of electrons following exposureto the ion beam.
 27. A method of changing a molecular structure of alignocellulosic material, the method comprising: exposing thelignocellulosic material to an adjusted ion beam as the material movespast the adjusted ion beam to cause chain scission of thelignocellulosic material, the adjusted ion beam having been produced byadjusting the energies of at least some of the ions of an ion beam basedon a thickness of the lignocellulosic material, the ion beam comprisinga first distribution of ion energies having a full width at half maximumof w prior to adjustment and a second distribution of ion energies inthe ion beam having a full width at half maximum of more than w afteradjustment.